eV , how much is it?

[studiot]

That's real fine, DrDoggy,

 

We are getting to what you are really after.

 

 

It does not matter what table you get you electron volt values from, they they should be the same since there is only one definition.

 

What you need to remember from a chemistry point of view is that every reactant and product is in a particualr state and the energy balance of the reaction reflects the energy required to place those reactants and products in that particular state, as well as the energy obtained from/supplied to the reaction.

Every table describes the state of the reactants and products (called standard conditions by that table).

You may need additional information to translate the reactants or products to the states in their final condition in the reaction equation.

Edited June 22, 2015 by studiot

[DrDoggy]

It has been very interesting learning about delta H, and how I need to apply the changes to each member in the Stoichiometry,

but which of these values is the ionization energy we were talking about?

 

gibbs free energy, I need to look at better, i think? that looks like my total power input? because it is the change of energy in system, minus the change of"disorder?"

 

Entropy also answered alot of things about what i didnt understand prior. and seems to describe my question earlier about dispersal of the systems, which im looking in to...To me it sounds like it is somewhere in the entropy equations i will find my volts required?

 

But i think im confused, gibbs energy is the work i get out of it, which implies the total energy in/out, which is: enthalpy, the change of energy in the system MINUS entropy, energy required to drive the system, is that correct? so with my laser and ionization energy i am really only looking at enthalpy?

 

Also I am happy that i did not confuse PV(pressure,volume) with PV(power,volts)!

Edited July 4, 2015 by DrDoggy

[studiot]

There is an awful lot to get your head around in this part of physical chemistry and it takes a lot of time and effort.

 

But you seem to be making real progress.

 

The thing to remember about energy is that there are lots of forms of energy and most can be converted from one form to another.

However Nature is not that generous because it exacts a charge for doing this and that is what quantities like Gibbs and Helmhottz energy and entropy are all about.

 

Ask about these when you are ready for a gentle introduction.

 

[DrDoggy]

yes pls! Ready! These are long questions , about what you say about the forms of energy, and how they equate.

 

I just want to make sure i am correct with the following, and understand properly, if that is the case then i think my head can wrap so far!:

 

"gibbs energy is the work i get out of it, which implies the total energy in/out, which is: enthalpy, the change of energy in the system MINUS entropy, energy required to drive the system"

Edited July 4, 2015 by DrDoggy

[DrDoggy]

ok, so it sounds like gibbs and hemholts are similar except that the second one has constant values,

also im cool with gibbs energy if my previous statement is true , which i will continue to assume,

 

Entropy is also very curious as most of the tutorials glaze over it, however this link was very interesting especially about micro-states, hint:

in regard to this i notice he uses the "horseshoe" , I doubt he is talking about ohms though

 

also i wonder about the rate of decay for a micro state, oh, that would be the thermal conductivity,

Also I am happy with PV coefficient now , =nRT, which explains how they relate,

 

but i am still not sure how ionization potential fits in to all of this

[Dodecyl Sulfobetaine]

well ,nice to see you make progress,then where to go next?

[DrDoggy]

I still wonder though, enthalpy and entropy as mentioned(thanks!) are total energy measurements, but how does that energy break down to its types, ie, heat , light, (sound im not too concerned) , also how are these emitted, ie, light emissions would be in certain spectra based on what?

 

OR same question: what forms is the energy transmitted when we talk about entalpy and entropy? ie is it via the kinetic energy that is described as temperature, where molecules bounce off each other, or via an infra-red band spectrum from emission?

 

Specifically in the case of my laser, any chem reaction that happens then reverses itself, so all we have is the energy loss from the photon being emitted from the ionization, but the heat generated from ionization should cancel out after the electron is readded. there for my laser should not get hot.

 

to me it sounds like , we are putting enough energy in to form ionizations, but then have put in additional energy that did not make it to the ionization point which releases as heat. Where does this heat come from? It seems to me that there should be a way to tune my energy input so that there is no excess heat and only light , but how could i do this? my first guess is that i should pulse my energy input at a specific time interval(frequency)., I have been thinking about this and it seems that if my pulse is too fast the energy will act as an xray and travel through , if it is too slow, this is where i get my heat, much like dc in a wire?

am i close with this?

Edited July 16, 2015 by DrDoggy

[studiot]

Thermodynamics was originally developed to study the relationships between thermal and mechanical properties, but was later extended to include other properties involving energy. Its laws and methods may be applied anywhere energy is involved.

 

Thermodynamic theory divides a universe into two parts: The ‘system’ and the rest of a universe. I say ‘a universe’, not ‘the universe’, because this includes everything of interest or relevant in a particular thermodynamic discussion, both inside and outside the system., but may exclude other parts of the Universe at large.

 

It displays an identifiable boundary between these two parts.

This boundary may be fixed as in a chemical reaction flask.

Or it may be part moveable, part fixed as in a piston in a cylinder.

Or it may be wholly moveable as in a balloon.

Further it may have physical concrete existence as in the above examples or it may be a theoretical surface such as the space surrounding a molecule.

Incorrectly/inappropriately specifying the boundary is a common source of difficulty.

So when considering the thermodynamics of heating some reagents in a flask or braker to form products,

The bunsen burner is part of the rest-of -the-universe (not the system). The flask is the fixed part of the boundary and the liquid surface the moveable part.

 

Finally a particular Thermodynamics discussion deals with a specified ‘Thermodynamic Process’ of interest.

This may be a single stage process and may involve the entire system.

For example blowing up a balloon.

Or there may be several processes in action in different parts of the system.

In this situation the system may be broken down into smaller subsystems, each with its own process, and sub boundary.

A process may be one-time or cyclic or may even be stasis (=Thermal Equilibrium).

 

Once we have defined the system, its boundary and the process involved, we can study the system properties.

There are directly observable variables such as pressure, volume, temperature, number of molecules, phase (solid, liquid, gas, dissolved) etc.

We also identify derived or calculable variables such as internal energy, entropy, enthalpy and so on. These variables are calculable using some of the many thermodynamic relations or equations that are known.

Some variables may be mathematically treated as constant for a particular system.

Examples would be specific heat, density, redox potential, ionisation potential.

A complete list of the values of the properties is called the State of the System.

We may equally apply this to the rest-of-the-universe and talk of the state of the rest-of-the-universe.

Since the above variables are define the state of the system they are called state variables.

 

Yet more variables have a particular and very important role to play.

These do not apply directly to either the state of the rest-of-the-universe or to the state of the system but to exchanges between the two.

These are hugely important and form the basis underpinning thermodynamic theory.

 

These variables act across the boundary so linking the system to the rest-of-the-universe.

 

Originally they were heat input and work extracted, but now the list has been extended to other forms of energy such as electromagnetic.

 

It is important to realise that heat and work are not state variables, and by themselves cannot define the state of anything.

Nor are they properties of the system.

 

On to part 2

Edited July 17, 2015 by studiot

[swansont]

I still wonder though, enthalpy and entropy as mentioned(thanks!) are total energy measurements, but how does that energy break down to its types, ie, heat , light, (sound im not too concerned) , also how are these emitted, ie, light emissions would be in certain spectra based on what?

 

OR same question: what forms is the energy transmitted when we talk about entalpy and entropy? ie is it via the kinetic energy that is described as temperature, where molecules bounce off each other, or via an infra-red band spectrum from emission?

 

 

Careful here: Entropy is not an energy. It has units of energy/temperature, e.g. joules/kelvin. TS is an energy term in the Gibbs free energy and Helmholtz free energy.

[DrDoggy]

I think what is really getting me with enthalpy here is "energy"?, are we saying energy in the form heat, or energy which could be heat?,

also are the other forms of energy included in the ^H,^S tables, or do they have seperate table?, (one i can think of is the spectroscopy table, which is obviously separate)?

I realize its measured in joules, which suggests energy, but then when the tutorial generalizes they throw the word heat in there.

which suggests that enthalpy breaks down to another equation?

[Sensei]

Imagine box with particles.

If you will add energy from external source, total energy of box will increase, particles will have higher kinetic energy.

Particles are bouncing back and forth from each other. Elastic and inelastic collisions.

There are also created photons, and absorbed photons.

The more total energy in the box, the higher temperature, and the more higher energetic photons are there (and escaping from box radiating energy in the all directions).

Check black body emission spectrum, how it relates to temperature.

Compounds and elements change state, from solid to liquid, from liquid to gas, from gas to plasma. All depends on given total energy/temperature.

Chemical compounds break apart if there is exceeded certain for them temperature (energy from external source arrived).

At high enough energy atom is ionized (few to few hundred eV),

and at even higher energy nucleus is separating.

f.e. to destroy Deuterium atom there is needed energy >2.2 MeV,

result will be free proton and free neutron.

Free proton has 938.272 MeV,

free neutron has 939.565 MeV,

and Deuterium nucleus has 1875.613 MeV (it's easy to remember this value remembering equal of fusion p+ + p+ -> D+ + e+ + Ve + 0.42 MeV (938.272 MeV+938.272 MeV-0.511 MeV-0.42 MeV = 1875.613 MeV)).

1875.613 MeV + ~2.2 MeV = 938.272 MeV + 939.565 MeV.

 

You can heat body/liquid/gas by shooting to it macroscopic objects (they will slow down and give their kinetic energy to body particles),

or use high energy particles accelerated to relativistic velocities..

or use high energy gamma photons.

You will receive the same effect.

Deceleration of fast particle/object. And transfer of energy to body.

Which in extreme conditions mean nucleus split, ionization, in less extreme destruction of chemical compound and change state of matter.

Edited July 20, 2015 by Sensei

[studiot]

Hello Dr Doggy, how did you get on with my post 33?

 

 

I wanted to get this started before I was away, but didn't manage that so made a start at the weekend after my return.

 

Yes Enthalpy is part of the story and intimately realted to heat.

 

The old name for Enthalpy is Heat Content and many Engineering tables still us this.

 

My part 2 would bring in all this.

 

[DrDoggy]

yes post 33 sits well, hope you enjoyed days off!, all this is starting to make very much sense, very much ready for part 2, thanks!

 

 

also i have been looking at cells closer now and as a side question wondering about electrolyte bridges, how do you get them wet without having them dissolve in to the solution? or* how do they conduct without being wet?

 

Also Sensi, I think i get it , you are saying that in my laser reaction is a net 0 - photon lost, BUT we need to sustain that heat average to keep the reaction active, and the heat generated from my laser that i need to water cool is just leakage for that container?

[studiot]

Dr Dy, please look at post#11 of this thread, to save me a deal of writing.

 

http://www.scienceforums.net/topic/90143-entropy-at-maximum/

Edited August 4, 2015 by studiot

[DrDoggy]

thanks again for all the help, I have been busy pondering these things and i think i understand basically how it is working , I know i have questions still, but not sure what they are!

 

Another thing that is crossing wires is what is ionization, we mentioned that when salt is dissolved in water it becomes ionized, then it conducts electricity, does the same hold true when we are talking about ionization energy, ie, if i were to ionize silicon, would that put it in to a conductive state?

 

also, if i do ionize silicon, by applying a certain volts + amps, and it is now conducting, how would I get to remove the second ionization shell?

 

maybe i am confused about this as well, but: when i think of ionization i think of +ve volts being applied to a material causing a static charge, without a ground, but that is contradictory to my knowledge of electrolysis where i would want a closed loop circuit, ?

[DrDoggy]

edit: how much volts amps, would I need to remove the second ionization shell, wouldnt the conductance of the "first ionizaton" particles cause current leakage making it harder to volt up?

[studiot]

Hello again DrDoggy,

 

You started this post because you were unsure about ionisation so perhaps we should start at the beginning.

 

Chemists regard molecules as the smallest lumps of matter. Molecules can be single atoms or connected groups of atoms. Normally they are electrically neutral, because although they contain positively and negatively charge sub atomic particles, they contain an equal number of each.

 

Ionisation is the process of creating charged molecules from these neutral ones.

This can happen in five ways. This can either be forced or some (unpreventable) natural processes can also cause ionisation

Taking away or adding either positive or negative charges accounts for four of these mechanisms.

Splitting a molecule into smaller charged molecules offers the fifth.

 

Charged molecules are called ions.

 

 

 

Post#21

Don't forge that ionisation energy and ionisation potential is defined to the removal of one electron from the free atom in a gaseous state.

 

 

Silicon is a semiconductor and a solid in normal circumstances so passing electric current through it by applying a voltage will not result in ionisation.

The application of increasing voltage from zero to a bar of silicon will simply show a small current increasing from zero with a roughly parabolic curve, until 0.6 volts habeen reached.

At this voltage the current increases dramatically as electrons are promoted to the conduction band.

Since electrons are supplied at one terminal of the bar, pass through the silicon in the conduction band and exit through the other terminal, electrons are never actually removed from the silicon atoms, and the semiconductor molecular lattice remains intact and overall neutral.

An example of ionisation by applying an electric voltage would be a discharge tube such as a flourescent light fitting.
Inside these once the ‘striking voltage’ is applied electrons are stripped from the molecules in the gas in the tube at one terminal and removed.
This creates positive ions which migrate towards the other terminal where they receive electrons and return to neutral molecules.

Edited November 5, 2015 by studiot

[DrDoggy]

oya, that also brings up another question, or2, like does negative ionization affect the molecules coheision the same way positive does? ie are negative ions more chemically stable?

also,heh, i have always wondered what would happen if a lightning strike hit a pvc tube full of water, would that split the H & O (if it didnt split the pipe)?

 

0.6v? isnt the first ionization potential of Si 8v?

 

That explination of ionizing gases makes sense but then what about in the terms of liquids/solids, such as water and our silicon and/or liquid salt, does this migration happen in these situations too?

[studiot]

 

0.6v? isnt the first ionization potential of Si 8v?

 

 

Silicon is a semiconductor and a solid in normal circumstances so passing electric current through it by applying a voltage will not result in ionisation.

 

 

Edit

Actually, to be fair, it is a somewhat disingenuous average to use 0.6 volts as the bandgap (= the forbidden zone) for pure silicon is 1.1 volts.

But silicon is usually doped.

 

 

In the solid state silicon is covalently bonded giant molecule, also called metallic bonding. It does not ionise with the passage of electricity, it merely heats up, through ohmic heating, and eventually melts to liquid silicon comprising covalent molecules or individual silicon atoms, both of which are neutral.

 

Solid state physics and chemistry is fascinating, but you are opening a big subject and adding phase diagrams makes things even bigger.

 

Do you want to proceed?

 

 

Edited November 6, 2015 by studiot

[DrDoggy]

maybe later on we could proceed with semi-conductors, but for now im still curious as to how conductors work in this situation, for example in a reaction similar to electroplating where my copper anode metal "Migrates" to the brass cathode, how would it go about?

 

ie:

1)first i charge my anode to the ionization voltage

2) the anode atoms then migrate to the brass cathode where they bind.

3) this reaction will use up current/power/ev based on reaction volume & time.

 

4) but what happens with the electrolyte, wouldn't having it cause conduction and therefore a "leakage current" ? Is there a way to minimize this loss/ or is there another way to compensate? (Or maybe im just over thinking)

 

5) also in this situation what if i wanted to multiply the production rate? would that mean doubling the current, which would mean doubling the voltage input?

 

also maybe i am confused about how to get to second ionization energy, am i mistaken that ionized particles dont necessarily conduct? for example , i charge my material to the first ionization voltage, it starts to conduct causing current, now how do i get to second ionization, is it just a matter of turning volts up to second ionization potential, will there be additional leakage current, (again maybe overthinking)

[DrDoggy]

Hi, still wrapping my brain around all this! and i think i get it now, but i keep hitting a wall, partially due to the fact that alot of the web confuses IP to be the same as IE,

 

so turning to the electrolysis of water i need at least 1.23 volt to start an electrolysis process, also i discovered a thing called overpotential, which says i actually need 1.5volt to overcome activation barriers

 

https://en.wikipedia.org/wiki/Electrolysis_of_water

 

does that mean my ionization potential is 1.23 volt?

and is that regardless to volume & size and more to do with electrode spacing?

and if so , how do i calculate volts required for x distance between electrodes?

 

thanks!

[John Cuthber]

Hi, still wrapping my brain around all this! and i think i get it now, but i keep hitting a wall, partially due to the fact that alot of the web confuses IP to be the same as IE,

 

so turning to the electrolysis of water i need at least 1.23 volt to start an electrolysis process, also i discovered a thing called overpotential, which says i actually need 1.5volt to overcome activation barriers

 

https://en.wikipedia.org/wiki/Electrolysis_of_water

 

does that mean my ionization potential is 1.23 volt?

and is that regardless to volume & size and more to do with electrode spacing?

and if so , how do i calculate volts required for x distance between electrodes?

 

thanks!

 

"so turning to the electrolysis of water i need at least 1.23 volt to start an electrolysis process,"

No.

(The wiki articles is misleading)

[DrDoggy]

how misleading?

[John Cuthber]

Wiki says "Electrolysis of water is the decomposition of water (H₂O) into oxygen (O₂) and hydrogen gas (H₂) due to an electric current being passed through the water. The reaction has a standard potential of -1.23 V, meaning it ideally requires a potential difference of 1.23 volts to split water."

 

The killer is the word "ideally".
Well, that number is easy to calculate.

You find a table like this

http://www.physchem.co.za/data/electrode_potentials.htm

and add up the potentials for the decomposition hydroxide ions and hydrogen ions.

The one for hydrogen is easy- it is zero by definition.

And the other one

O2 (g) + 4H+ + 4e- 2H2O

is near the bottom of the table.

 

Fine, except that those are standard potentials. The pressure of the gases is 1 atmosphere and the concentration of the ions involved is one molar.

But real water doesn't have 1 mole of hydrogen ions per litre: it's about a ten millionth of that.

On the other hand, the first traces of oxygen and hydrogen released at the electrodes don't need to exert 1 atmosphere of pressure- they can simply dissolve.

And in real water there's usually enough dissolve oxygen that the reaction isn't production of hydrogen- it is the reduction of dissolved oxygen

 

People think that 1.23 volts is some "magical" figure that is correct in all circumstances. it's just not true- it's easy enough to prove it with a meter, two electrolysis cells in series and a single 1.5 volt battery.

Since there are two electrolytic cells and the battery only produces 1.5 volts, the cells must each have 0.75 volts across them.

Yet a current will still flow- typically a very small one unless you have big electrodes close to eachother.

If you wan to calculate the equilibrium voltages you need something like this

https://en.wikipedia.org/wiki/Nernst_equation

and it gets even more messy if you want to take into account the effects of a current flow.

 

 

And all of this has essentially nothing to do with ionisation potentials which are generally measured for single atoms or molecules in the gas phase.

[DrDoggy]

ack! I'm very sorry guys you keep mentioning that it is only for gas phase, idk why i keep blocking it out! thanks again for all the patience!

 

Yah, I get basically what you are saying with the nerst eq, but only basically, all the numbers get me lost , and mostly only understand in relationship from my electronics edu on cells.

Actually I'm also interested in the effects of a current flow, but please just a simple description, it also brings up a question for me about things like different flows and potentials at different points.... and how fast do they travel...is it related to the em wavelength and speed of light

Edited May 20, 2016 by DrDoggy